package com.burial.common.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Component
@Slf4j
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWhitLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }


    public <R,ID>R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R>dbFallback,Long time, TimeUnit unit){
        String key=keyPrefix+id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否为空字符串
        if (json!=null){
            //返回错误信息
            return null;
        }

        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        if (r==null){
            //将null写入null
            stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL,TimeUnit.MINUTES);
            //5.不存在，返回错误
            return null;
        }

        //6.存在，写入redis
        this.set(key,r,time,unit);
        //7.返回
        return r;
    }

    /**
     * 开启10个线程池
     */
    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);

    /**
     * 利用逻辑过期解决缓存击穿问题
     * @param id
     * @return
     */
    public <R,ID>R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID,R>dbFallback,Long time, TimeUnit unit
    ){
        String key=keyPrefix+id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isBlank(json)){
            //3.不存在，直接返回
            return null;
        }
        //命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //未过期，直接返回
            return r;
        }
        //已过期，缓存重建
        //获取互斥锁
        String lockKey=RedisConstants.LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //互斥锁获取是否成功
        if (isLock){
            //成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                //重建缓存
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);

                    //写入Redis
                    this.setWhitLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }

        //返回过期的商品信息
        return r;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10L, TimeUnit.SECONDS);

        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

}
